1. Field of the Invention
This invention relates to a step-by-step motor able to carry out up-and-down transmission, particularly to one convenient and quick in assembly and able to carry out transmission with steadiness and with less noise.
2. Description of the Prior Art
The headlamp of an automobile is generally provided with a step-by-step motor for adjusting the level of the headlamp. A conventional step-by-step motor 1, as shown in FIGS. 1 and 2, includes a housing 10 formed with an accommodating chamber 100 having a recessed chamber 101 disposed therein. The recessed chamber 101 is formed with an insert hole 102 in an upper wall and extending down to the topside of the housing 10 and having a side wall provided with positioning engage notches 103. The housing 10 has a topside bored with an insert groove 104 and outer wall fixed thereon with a plurality of engage projections 105. A driven gear 11 to be received in the accommodating chamber 100 of the housing 10 has topside mounted with a connecting block 110 with an insert hole 111 that has a lower portion provided with female threads 112. A worm gear 12 positioned at one side of the driven gear 11 has a topside set with a transmitting gear 120 engaged with the driven gear 11. A top rod 13 is inserted through both the insert hole 111 of the driven gear 11 and the insert hole 102 of the housing 10, having a lower portion formed with male threads 130 to be screwed with the female threads 112 of the driven gear 11. Further, the top rod 13 has an outer wall fixed thereon with plural lengthwise projections 131 to be respectively fitted in the positioning engage notches 103 of the housing 10 and a lower side provided with an interacting block 132 with an engage notch 133. A transmission motor 14 to be installed in the accommodating chamber 100 of the housing 10 is provided with a worm 140 engaged with the worm gear 12. A circuit board 15 assembled in the accommodating chamber 100 of the housing 10 and located at one side of the transmission motor 14 is provided with a position-limiting switch 150 having a sidewise rod 151 fitted in the engage notch 133 of the top rod 13, also disposed thereon with a bayonet socket 152 aligned to the insert groove 104 in the topside of the housing 10. A cover 16 to be covered on the bottom of the housing 10 has an outer wall bored with a plurality of engage grooves 160 to be respectively engaged with the engage projections 105 of the housing 10, thus finishing assembling a conventional step-by-step motor 1.
In using, after the worm gear 12 is actuated to rotate by the worm 140 of the transmission motor 14, the transmitting gear 120 on the worm gear 12 will drive the driven gear 11 to rotate and actuate the top rod 13 to move upward or downward, and thus the top rod 13 connected with the headlamp can adjust the angles of the headlamp. When the top rod 13 is actuated by the driven gear 11 to move upward or downward, the interacting block 132 at the lower side of the top rod 13 will drive the sidewise rod 151 of the position-limiting switch 150 on the circuit board 15 to move upward or downward. Thus, the elevation angle of the headlamp can be adjusted and fixed in position.
However, the conventional step-by-step motor 1 functions to carry out up-and-down transmission by means of mutual engagement and relative motion of the worm 140 of the transmission motor 14 with the worm gear 12 and the transmitting gear 120 on the worm gear 12 with the driven gear 11. Thus, after used for a long period of time, the gears are easy to be worn off and may produce tooth leap, unable to carry out transmission steadily and likely to make great noises. In addition, the conventional step-by-step motor 1 is complicated in structure and hard to be assembled.